This invention relates generally to fuel systems for gaseous fueled engines. More particularly, but not by way of limitation, this invention relates to improved apparatus and methods for controlling the air to gas ratio of fuel supplied to gaseous fueled engines.
U.S. Pat. No. 4, 512,304 issued Apr. 23, 1985 to Warren E. Snyder illustrates one method and apparatus for controlling air to gas ratios in gaseous fueled engines. That system functions satisfactorily. The system described hereinafter is an improvement to the system described in the '304 patent.
Often, gaseous fueled engines are used as an industrial engine, that is, they are applied in situations where their operating speed is constant. In such installations, it is highly desirable that the operating speed be maintained despite variations in the load that occurs thereon and despite the use of different fuels. Frequently, alternate fuels such as sewage gas and natural gas are available which have significantly different heating values.
In the usual constant speed industrial engine, the application of increased load to the engine results in a slowing of the engine, and if the load is sufficiently high, may result in stalling of the engine. When the decrease in engine speed occurs, it takes a relatively long period of time for the engine to return to its desired operating speed.
Changing to a fuel having a lower heating value may also have a significant momentary effect on the operating speed of the engine. In such instances, the operating speed of the engine will drop and again, substantial time is required for the engine to return to its operating speed.
Accordingly, an object of this invention is to provide a fuel control system for a gaseous fueled engine that can be used with fuels of different heating value and under varying loads, and yet maintain the engine speed as a result of those changes as nearly constant as possible, while at the same time maintaining the air to gas ratio of the fuel at the desired value when the engine is at operating speed and under the normal loading.